<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
  <style>
    [v-cloak]{
      display: none;
    }
    
  </style>
</head>
<body>


</body>
<script src="js/JQuery-2.1.4-min压缩.js"></script>
<script>
  
  function queryData(url) {
    return new Promise(function (resolve,reject) {
      var xhr = new XMLHttpRequest();
      xhr.onreadystatechange = function () {
        if(xhr.readyState !== 4) return
        if(xhr.status === 200){
          resolve(xhr.responseText)
        }else{
          reject('出错了！')
        }
      }
      xhr.open('get',url)
      xhr.send(null)
    })
  }
  
  queryData('http://localhost:3000/data')
    .then(function (data) {
      console.log(data)
      return queryData('http://localhost:3000/data2')
    })
    .then(function (data2) {
      console.log(data2)
      return queryData('http://localhost:3000/data3')
    })
    .then(function (data3) {
      console.log(data3)
    })

  


</script>
</html>
